crypto: blake2s - move update and final logic to internal/blake2s.h

crypto: blake2s - move update and final logic to internal/blake2s.h

Move most of blake2s_update() and blake2s_final() into new inline
functions __blake2s_update() and __blake2s_final() in
include/crypto/internal/blake2s.h so that this logic can be shared by
the shash helper functions.  This will avoid duplicating this logic
between the library and shash implementations.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>